1. Field of the Invention
The present invention relates to a method of anterior cruciate ligament (ACL) reconstruction and, more specifically, to a method a ACL reconstruction using a pin formed of allograft bone material.
2. Description of the Related Art
When a ligament or tendon becomes detached from associated bone, surgery usually is required to re-secure the ligament or tendon. Often, a substitute ligament, or graft, is attached to the bone to facilitate re-growth and permanent attachment. Various methods of ligament graft attachment are known, including staples, suture over buttons, and interference screw fixation.
Staples and suture buttons are disadvantageous because they often do not provide fixation sufficient to withstand the normal tensile loads. With suture button fixation, for example, a strand of suture couples the button and the substitute ligament. This strand becomes the xe2x80x9cweakest link in the chain,xe2x80x9d and if the strand breaks, the ligament detaches.
A stronger graft attachment can be obtained by interference screw fixation. An interference screw is used to wedge a graft bone block to the wall of a graft tunnel. See, e.g., U.S. Pat. Nos. 5,211,647, and 5,603,716, incorporated herein by reference. Although interference screw attachment is more secure than using staples or suture buttons, it is sometimes neither possible nor desirable to provide such fixation, particularly in the femoral tunnel. In revision situations, for example, where a previous reconstruction has been performed, placing a second femoral tunnel close to the previous tunnel may not be indicated.
In other cases, a semitendinosus graft must be used because the previous reconstruction used the mid third patellar tendon. Although a bone-semitendinosus graft-bone construct may be prepared using a workstation as disclosed in U.S. Pat. No. 5,397,357, the procedure is time consuming, and may be undesirable for other reasons.
A fixation technique which provides strong attachment of a semitendinosus graft in the femoral tunnel, using a transverse pin, is disclosed in U.S. Pat. No. 5,601,562, of common assignment with the present application. The transverse pin is inserted through a loop in a tendon graft. A threaded portion of the pin screws into the bone as the pin is advanced with rotation into the repair site. The technique is disadvantageous, however, because the graft can wrap around the pin as it is rotated. An improved tendon loading technique is the subject of U.S. Pat. Nos. 5,918,604 issued Jul. 6, 1999 and 6,132,433 issued Oct. 17, 2000.
An implant with back-biting threads has been developed as disclosed in U.S. Pat. No. 5,895,425 issued Apr. 20, 1999, also incorporated in its entirety herein by reference. The implant can be installed by impaction and so overcomes the graft-wrapping problem.
The need exists for methods of tendon repair that utilize surgical implants made of biologically-derived materials, such as allograft bone material, whereby biologic implants can be installed as transverse pins and can support tendon grafts.
The present invention overcomes the problems of the prior art and fulfills needs such as those noted above by providing a surgical bone implant made of allograft (or synthetic) bone. The implant preferably is formed of allograft cortical bone, and has a tapered tip with an eye for receiving suture. The implant can be advanced into bone by impaction. The implant is useful for various surgical indications, including fixating tendon grafts in a joint using the implant in a transverse, intraosseous application. Preferably, a looped graft is fixed in a bone socket by inserting the implant through the loop in the graft. The implant spans the bone socket clearance and is supported by the side walls that bound the socket opening.
The bone implant has a shaft with distal and proximal ends. For ease of insertion, the tip of the shaft is tapered. The remainder of the shaft is smooth and cylindrical. An eye for attachment of a suture is provided on the tip, preferably in the form of a 2 mm hole drilled through the tip. Suture is used to pull the implant into position. Axial grooves are formed on either side of the tip and intersect with the suture eye to provide clearances for a length of suture looped or knotted through the eye. Accordingly, the suture will not bind in the bone openings as the implant is urged into position.
The preferred implant is 5 cm long and is about 3-5 mm in diameter. The implant is of sufficient flexural strength and/or toughness to support a tendon graft loop using the implant installed as a transverse pin.
As applied in the knee, a method of using the implant includes the use of standard techniques to drill a longitudinal tunnel in the tibia. Subsequently, a femoral socket is formed, preferably in the lateral femoral condyle. According to the present invention, forming the socket is preferred to forming a tunnel through the lateral femoral cortex. Advantageously, the diameters of the tibial tunnel and femoral socket are made just large enough to accommodate the graft in a snug fit.
A tunnel hook, mounted on a cross-pin drill guide, is inserted through the tibial tunnel and into the femoral socket. A drill pin directed by the drill guide is drilled through the femur to intersect the femoral socket. The drill pin passes through the capture slot of the tunnel hook.
A hole then is formed in the femur, preferably using a cannulated drill placed over the guide pin, to accommodate the transtibial implant. Preferably the diameter of the hole is such that the pin will fit snugly in the hole.
Next, a flexible strand, preferably a wire formed of nitinol, is attached to the guide pin and pulled transversely across the femur, a portion of the strand passing through the capture slot of the tunnel hook. The ends of the strand protrude from the medial and lateral sides of the femoral shaft. With the strand ends secured to prevent accidental pull-out, the tunnel hook is withdrawn axially from the femoral tunnel, the strand being captured in the slot of the hook to form a strand loop that is pulled through of the socket and into the tunnel.
The hook is retracted completely, through the femoral socket and out of the tibial tunnel, such that a loop of the flexible strand protrudes from the entrance to the tunnel. Free ends of the strand remain exposed on either side of the femoral shaft.
The graft is passed through the diverted loop of the flexible strand. The loop is retracted into the femoral socket by pulling evenly on the medial and lateral ends of the strand. As a result, the graft is drawn into the socket.
A length of suture is attached at one end to the flexible strand and at the other end to the implant. The flexible strand is used to draw the suture into the femur. Additionally, the implant also can be impact driven into place. The implant passes under the tendon across the femoral socket, and coming to rest with either end of the implant supported in the femoral bone, thus securing the graft in the femoral socket.
Tibial fixation of the graft can be performed by various known methods, including interference screw fixation, which provides the most secure post-operative result; distal fixation with a cancellous screw using a post and washer technique; and a belt buckle staple technique utilizing a pair of ligament staples. As a further alternative, tibial fixation is achieved by way of the transverse pin implant described above for the femur, and femoral fixation is by one of the other known methods.
An alternative method of tendon loading is also provided for a closed-loop graft reconstruction. According to the alternative method, a flexible line is joined to one end of the strand. A strand/line loop is formed so as to protrude from the entrance to the tibial tunnel and present the junction between the strand and the line. The strand and the line are dejoined, opening the strand/line loop to accept the graft. The strand and line are rejoined so as to capture the graft, and the procedure continues substantially as set forth above.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. For example, although the description herein relates to ACL grafts and forming femoral tunnels in the knee, it will become apparent that expanded indications for the inventive method include other joints and replacement of other ligament or tendon structures using various types of graft constructs.